The present invention relates to a photographic camera having a shutter release mechanism.
Photographic cameras that record images on a perforated strip of photosensitive film are well known. Examples of such cameras include single lens reflex cameras (SLR), so-called xe2x80x9cpoint and shootxe2x80x9d cameras and recyclable cameras such as the Kodak MaxHQ (TM) camera. Each of these cameras captures an image of a scene by focusing light from the scene to form an image at the filmstrip. A movable shutter is disposed between the scene and the filmstrip. This shutter controls the amount of light to which the film is exposed. The shutter is normally biased to a position that blocks the flow of light from the scene to the filmstrip. Exposure of the film occurs when the shutter is moved to permit light from the scene to reach the filmstrip. In certain low cost cameras, a lever is used to drive the shutter against the bias so that light can pass between the scene and the filmstrip during exposure.
To prevent inadvertent movement of the shutter between intended exposures, the bias applied to the shutter is large. Accordingly, the lever must apply a significant force to drive the shutter into the exposure position. Often this force is supplied by a resilient member. The resilient member urges the lever toward contact with the shutter. Between exposures, the lever is urged away from the shutter and potential energy is stored in the resilient member. This process is known as cocking the lever. Once that sufficient potential energy is stored in the lever, the lever is locked to prevent the inadvertent release of the stored energy. An exposure occurs when the lock on the lever is released. Accordingly, cameras incorporating such a lever must provide a mechanism for cocking the lever against the biasing force supplied by the resilient member and for locking the lever against biased motion until the time of the next exposure cycle.
Typically, in relatively inexpensive still-picture cameras, the action of winding the film is used to cock and lock the lever. During film winding, a film take-up spool is manually rotated to advance successive frames (imaging areas) of the filmstrip from a light-tight cartridge across the focal plane of a taking lens and onto the take-up spool. Each time that the take-up spool is manually rotated, an unexposed frame of the filmstrip is positioned at the focal plane of the taking lens and an exposed frame is wound onto the take-up spool. In such cameras, a cocking structure is often provided to translate a portion of the energy from the winding operation to cock the lever. A locking structure is provided to hold the lever in the cocked position. The user releases the lock to initiate an exposure.
In the prior art, various structures have been used for the purpose of cocking and locking a lever during film winding and for releasing the lever during exposure. Examples of such prior art structures are shown in U.S. Pat. Nos. 3,394,643, 3,633,477, 3,673,941, 4,681,416 and 4,949,111. These structures while effective for their purpose are complex and a more simplified structure is preferred for use in less expensive, lightweight and recyclable cameras.
As is described in U.S. Pat. No. 3,906,570 one way to simplify the structures used to cock and lock the lever is to use the film strip in the cocking and locking the lever. An attendant risk with such a system is that the film will be damaged by the forces that it is required to convey in such use. Further, there is a risk that when the lever lock is released, the film will react by moving slightly. This causes the film to move at exactly the same time as the exposure resulting in a blurred image. The ""530 patent and 450 application shows a simplified structure that is intended to resolve this problem. However, what is still needed is a more simplified structure for integrating the winding operation with the cocking and locking operations. What is also needed is a simplified structure that performs cocking and locking functions and that further integrates a structure for releasing the lock.
The invention relates to a shutter release apparatus for use in a camera for capturing images on a perforated film. The shutter release apparatus has a rotatable thumb wheel movable along an axis between a start position and a trigger position. A sprocket is provided having teeth to engage perforations on the film and to move therewith during film winding. A biased lever is moved by the sprocket against the bias from a position holding the thumb wheel in the start position to a position releasing the thumb wheel for urged movement into the trigger position. The thumb wheel blocks biased movement of the lever when the thumb wheel is in the trigger position and movement of the thumb wheel from the trigger position to the start position releases the lever for biased movement to drive the shutter to expose the film.
In another aspect, a shutter release apparatus is provided for use in a camera for capturing images on a perforated film, the apparatus has a rotatable thumb wheel urged for movement between a start position and a trigger position. A sprocket is provided having teeth for engagement with perforations on the film and movement therewith during film winding. A biased lever holds the thumb wheel in the start position and is moved against the bias by movement of the sprocket to a position permitting the thumb wheel to move into the trigger position. The lever further defines a catch positioned to block movement of the sprocket when the film is advanced by a predetermined amount. Rotation of the thumb wheel in the trigger position further moves the lever against the bias. Movement of the thumb wheel from the trigger position to the start position releases the lever for biased movement to drive the shutter to expose the film.